A servo motor for moving a load is controlled by a controller for controlling, using a drive current or control signal, the servo motor which drives a mechanical load. The controller and the servo motor are implemented as a closed loop system. The controller generates a control signal instructing the motor to move the mechanical load. The control signal applied depends on the motion application type (motor is moved to a desired position at a desired velocity, motor speed is varied, or the torque applied is varied). A feedback signal from the motor to the controller indicates the current actual state (e. g., position, velocity, etc.) of the motor and/or load. The feedback signal can be originated by an encoder or a resolver attached to the motor, by measuring the load position, or by estimation. The controller then compares the actual position of the load (feedback signal) with the instructed target position (control signal), and adjusts the newly calculated control signal as needed to minimize the differences between both signals (actual and target positions). This is continued until the target position is reached.
Thus, at the beginning of a movement, the motor/load accelerates/decelerates, i.e. changes speed, in order to reach the target position. After that, the motor/load requires a so-called stabilization time which can be defined as the period of time required by the motor to reach a halt status of the motor/load after having arrived at the target position.
Further, in the controller, gain affects the accuracy (i.e. how close to the desired speed or position the motor's actual speed or position is). A high gain will allow an accurate movement. In order that the motor will perform without excessive overshoot and settle within adequate time periods, the servo motor is tuned, including the tuning of the servo motor's proportional speed gain.
The controller may implement for example a PID filter for calculating the control signal that is applied to the motor. When tuning the servo motor, parameters of the PID filter are tuned. These parameters may include the proportional speed gain, a proportional position gain, a velocity control gain, the torque command filter and a position command filter. The proportional speed gain may be understood as the primary parameter. The responsiveness of the servo motor (stiff or soft) is determined by the proportional speed gain.